Bias and Millon clinical multiaxial inventory (MCMI-II) diagnosis

In the current study, the degree of bias is calculated for each of the personality disorder and clinical syndrome scales of the MCMI-II. In general, most of the MCMI-II scales are prone to only mild or moderate biases. However, the paranoid personality disorder, somatoform, bipolar: manic, thought disorder, and delusional disorder scales are prone to severe biases. When the MCMI-II is utilized to make diagnostic decisions, bipolar and schizophrenic disorders are apt to be grossly underestimated. The implications of bias in diagnostic prevalence rates are discussed and an equation is offered which provides for adjustments to be made when the percentage of positive MCMI-II test results are used to determine prevalence rates for clinical or research populations. The observation is made that imperfect sensitivity and specificity for the MCMI-II scales will result in inaccurate estimates of personality disorders and clinical syndromes when the MCMI-II is used to survey various populations.